No problem with someone travelling in F to take in a guest to the CCR. In my experience, sometimes the staff on the desk try to insist that the guest is on the same flight as the F passenger, however, this is not the rule - the guest can be on a different flight (longhaul, shorthaul, domestic, whatever). If the person on the desk tries to pull this, ask for a supervisor (although they'll usually allow a "one time exception" at this point).